Email applications have become a dominant means of communication over the years. Email has been increasingly pervasive, and is commonly used among users within business. Email threads are used to help organize emails by relating an initial email to a series of reply emails resulting from the initial email. Email threads also provide context to a user by enabling the user to view the initial email and the subsequent chain of reply emails.
One problem with email thread is that oftentimes, there can be multiple email threads on a particular topic at different times or on different mailing lists. For example, a topic on how to get a simple Java Persistence Application Programming Interface (JPA) sample might be discussed in one month in one email thread but might again be discussed at a later month in a separate email thread. In another example, a sender might initiate two separate email threads on a particular topic at the same time, for example, where there is a vote email thread for project A 1.0 and a separate discussion email thread for project A 1.0. Two or more email threads such as these are often closely related but hard to locate without performing a search on a user's mailbox. Search can take a significant amount of time if a given user has a mailbox with many emails, especially when the user subscribes to one or more high-traffic mailing lists.
Another problem with email threads is that oftentimes a user might send an email with a discussion topic to a few recipients, and the user might later receive multiple open replies and some private replies. When the user replies, the user can reply only to one particular email thread with no indication of the user has also replied some other email threads that the user has received.